1. Field of the Invention
The present invention relates to a new and improved unitary, rigid, drop-in type filter for use in a high temperature, high pressure application in a pyrotechnic air bag inflator. More particularly, the filter is particularly designed to withstand the high temperature and high pressures encountered from contact with gas generated in a pyrotechnic air bag inflator from gas generating material such as sodium azide wafers. The filter functions to cool the hot gases before they reach the air bag and serves to eliminate and trap particulates and residues generated during ignition so that they do not enter the air bag and contaminate the vehicle.
2. Background of the Prior Art
In prior pyrotechnic air bag inflators, metal wire mesh or screen has been used to filter the gaseous flow emanating from the combustion of the pyrotechnic materials of an air bag inflator, before the gases enter the air bag. Japanese unexamined Patent Publication No. 50-48797 discloses an air permeable trap or filter of granules or particles used to screen or filter gaseous flow from an air bag inflator before the gas enters the air bag.
A major concern in pyrotechnic type air bag inflators is that the expanding gas generated for inflation of an air bag is so high in temperature that burning of the air bag or injury to an occupant occurs when the air bag is inflated. Sometimes, pyrotechnic material is ignited to generate high temperature gas which contains impurities such as molten or gaseous metals and oxides which are toxic and cause damage to the human body.